The invention relates to a seal for a dynamic mixer. Such a dynamic mixer is in particular used in the mixing of a plurality of viscous or pasty components such as impression materials in the dental sector, two-component adhesives or sealing materials.
A dynamic mixer is known from WO 2007/041878 for mixing components having different volume proportions, in particular for manufacturing dental impression materials. An antechamber is arranged in the inner space of the mixer housing within which the mixing rotor has a distribution body for distributing the components about its axis of rotation in order thereby to achieve a correct mixing ratio between the components and to avoid air inclusions. Subsequently, the premixed components move into a main chamber through at least one passage opening for their complete mixing.
Since the components react with one another and harden in the mixer on an interruption of the dispensing, the mixer must be replaced and disposed of after use together with the components contained therein. The components can in particular move into the intermediate space between the mixing rotor and the cover of the mixer housing, and indeed exactly at that point at which the mixing rotor is supported in the cover. For this reason, a sealing lip which is arranged downstream of the bearing location is provided in WO2007/041878.
However, it has proved to be disadvantageous in the embodiment in accordance with WO2007/041878 that the components entering into the intermediate space between the cover and the mixing rotor through the inlet openings can move into the intermediate space between the sealing lip and the inner wall of the cover, can remain there and can react uncontrollably with one another. Reactions of this type can vary the consistency of the components and impair the mixing performance as well as cause inhomogeneity in the mixture. When such components harden on longer contact, clumps may be formed which are undesired in the mixture, which impair the quality of the mixture or which even allow the mixture to become unusable. Such a clumping can also impair the operation of the mixer with a sufficient size in that the intermediate spaces between the mixing rotor and the housing are clogged. The mixer can thus even become unusable.